Stubborn external HD won't mount. Any tips?

My 200 Gig LaCie firewire external is having some issues. First of all, I think the powersupply is failing because it doesn't turn on 90% of the time. The times I do get it to turn on, it won't mount on my powerbook. I've opened up disc utility and the HD is nowhere to be found. Anyone know how to get a stubborn external HD to mount?

I'm looking into getting a new case. I didn't know that was even possible with these external HD's. Thankfully, this morning the drive did turn on and mount, and I managed to copy my data. All my important files & pics are safe. This could have been a lot worse.

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